chore(deps): bump @docusaurus/preset-classic

Bumps [@docusaurus/preset-classic](https://github.com/facebook/docusaurus/tree/HEAD/packages/docusaurus-preset-classic) from 2.0.0-alpha.69 to 2.0.0-alpha.70.
- [Release notes](https://github.com/facebook/docusaurus/releases)
- [Changelog](https://github.com/facebook/docusaurus/blob/master/CHANGELOG-2.x.md)
- [Commits](https://github.com/facebook/docusaurus/commits/v2.0.0-alpha.70/packages/docusaurus-preset-classic)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]